Magnetic Chucks?

[randyjaco]

Well this old Enco surface grinder is starting to look like I may have it close to working order. The next challenge is a magnetic chuck. Being new to surface grinding, I have no idea of what to look for. I am going to need a 6x18 and that is about the extent of my knowledge. The SG has the capacity for an electro magnetic type. What are the pros and conns of permanent magnet vs electromagnetic? Enco has an import 6x18 permanent magnetic one for @$500. The next step is way over a grand. Ebay has them all over the place, from $300-$3k.

Now this is going to be a hobby machine and my budget is tight ($300-$700). Does anyone have some words or wisdom to help me select an adequate magnetic chuck for this beast?

TIA

Randy

[moldmonkey]

A drawback to a permanent magnet is that turning the on/off handle (like a mag base but a long handle) sometimes interferes with the work on the table if the work/fixture overhangs on the operator side. A prime example would be using a Spindex on the surface grinder. You can work around it, it is just a PITA.

[Carld]

Try to get a mag table with narrow poles rather than wide poles. It holds better and works with small parts better.

[easymike29]

I am assuming your grinder is a 6X18. Unless most of your work needs the 18 inch chuck it is best to install a 6X12. Cheaper, lighter and safer. Easier to grind into truth. More finger clearance when grinding in grooves. Just because a grinder has 18 inches of travel does not necessarily mean that you should have an 18 inch chuck.
Gene

[easymike29]

A drawback to a permanent magnet is that turning the on/off handle (like a mag base but a long handle) sometimes interferes with the work on the table if the work/fixture overhangs on the operator side.

You can replace the supplied handle with one of your own made from hex material which can then be activated with a box end wrench or ratchet arrangement. Design to your taste.

Gene

[Bill Pace]

I think easymike has a point there with the 18" magnet -- you mention it being for HSM and the 18"ers are getting sorta out of the usual HSMers 'range. If it is indeed a 6x18 grinder, then a 6x12 mag should be more than ample for home shop use.

Also the advice on a fine pole mag is right on, they will hold those little parts whereas the conventional poles sometimes wont.

As you said, mags are usually pretty common on ebay and you should be able to pick up a 6x12 under $150 with a little patience. I got a nice 6x12 fine pole for $108 and the guy even shoehorned it into a mail priority box and sent it for $10, - my mail lady didnt care for that!

[oldtiffie]

Good grinding

All good points.

I have several smaller grinders (about 12 x 6) than the Enco, but the principles are the same. They are plenty big enough for anything I have to do in my HSM shop. I always take my magnetic chucks off the grinder when not in use as they are fairly heavy - but "lift-able" - as I have ball-type rollers under my table in two rows. One row is in a "Vee-way" in the moving table and grinder base and the other "way" is flat. I don't like a lot of weight on my "ways" as the balls may indent them - especially so as my grinders are each on a bench-top with another machine which will transmit vibration to the grinder/s.

Here is my surface grinder with a magnetic chuck as well as a "Spindexer" on it.



The "On/Off" lever is really just a large long hex/"Allen" key. I have never had any problems with the lever but if I did I'd use a standard hex/square adaptor for a socket-set.

I prefer a permanent magnet type as I can regulate the "pressure/pull" with care whereas an electric unit is either full on or full off.

It is important to get the grinder and the magnetic chuck "ground in". As soon as I had my grinders installed, I set up and dressed a good "medium" wheel and took a very light cut over the table where the chuck was to sit. I always leave a "witness" and take the least possible off - which should be a "one off" for that machine.

I can tell you that neither of my magnetic chucks were accurately flat or parallel - as I expected - and as I required.

I put the working/top face of my chuck on the bed for it on the table (Ie base upward for grinding it), packed/shimmed it so that it did not move then only lightly put the magnetic field/switch on and re-checked. I took a series of fairly light cuts (say 0.002") gradually - pausing if the chuck got warm - until I had only a small witness mark left. I let the chuck cool right off, re-dressed the wheel and took a last/final very fine finishing cut. The base of the chuck was now flat and not too far out of being parallel with the top of the chuck.

I removed the chuck from the table, cleaned its base and the table where it was to be mounted, then mounted the chuck onto the table ("working face" upward) with bolts (using the table t-slots) and clamps and proceeded to grind the top of the chuck - as for the base.

The top of the chuck was now flat and parallel to the base of the chuck, the top of the table and the "ways" of the grinder.

Every time I mount a chuck onto the grinder I run a good test dial indicator over it - end-to-end and side-to-side as well as across it at the ends and centre. It is very close indeed - never more than 0.0002" - so I have never had to re-grind the top of the chucks as both chucks are used on three grinders - so that is a good check.

The "wider" spaced pole chucks are cheaper and it is your choice as to whether closer-spaced pole chucks are better value for your purposes. I did buy quite few of the closer-spaced pole adaptors for my chucks but I rarely use them. They are at (search term: magnet):
http://www.cdcotools.com

Your chuck will have metal adjustable "fences" on at least one end and one side - they are there to be used to stop stuff flying off the chuck (usually small and/or thin stuff). You can and should use thin steel strips on the chuck as "stops" as well - for round small work, form the strips into a "vee" shape (as for a "vee" block) and use them as stops.

Do not use "blunt" wheels as they will "burn" - and possible distort - the work. Dress the wheel as often as necessary. If you have coolant - use it.

I don't use "fine" wheels unless really necessary as they are slow to use and more prone to "losing their edge" and of burning the work and also in more frequent need of (re)dressing - PITA.

I will use the coarsest wheel that I can.

A "finer" finish is not necessarily flatter or "better" than a coarser finish.

If you have a balanced/balancing hub for your wheels - use it, as that, as much as finer wheels, will give you a much better finish if set up and used correctly. Re-check the wheel balance periodically as wear and dressing will cause a progressive loss of balance.

I would guess that the spindle on your grinder is 1 1/4" (31.75mm) as that is a standard for "Tool Room" and commercial surface grinders.

There are a huge variety of wheel type, shapes, materials and sizes available.

I use a fine medium and coarse grade wheel in aluminium-oxide (general use and for HSS tools), silicon carbide (for TC "tipped" tools); "hard ("blue")" wheel in place of cubic boron as well as cubic boron and diamond to TC tools as required (the hard, cubic boron and diamond will last for ages with proper care).

A good wheel guide is at:
http://www.ind.nortonabrasives.com/M...References.pdf
http://www.ind.nortonabrasives.com/
http://www.ind.nortonabrasives.com/D...00000000001823
http://www.ind.nortonabrasives.com/D...89&DTY_N_ID=-1

[Henro]

I prefer a permanent magnet type as I can regulate the "pressure/pull" with care whereas an electric unit is either full on or full off.

Just a small point, but I think you inadvertently got this backwards...I don't have an electric unit, but from what I have read the pull on the electric unit is adjustable, by varying the current through the electromagnets, while most use their PM chucks either in the full-on or full-off position.

This leads into the question, I wonder if any of us use their PM chucks in a position between full on and full off? Seems like there is a range of magnetic pull between the two positions, at least on my chuck. It never occurred to me to obtain variable pull by setting the PM chuck somewhere between full on and full off...

How many actually do this with a permanent magnet chuck?

Mabye Oldtiffie is doing this...first I have heard of this, but that is not unusual...I am usually the last to know...

[randyjaco]

Thanks Guys, especially to Tiffie for his excellent tutorial. That is the kind of stuff that just doesn't show up in the books.

I like the 6x12 idea, if nothing else it will save me a bundle on shipping.

Randy

[pcarpenter]

I know the last post was a few days ago, but wanted to offer a data point. I ordered one of the fine pole chucks from CDCO tools at what appears to be a bargain price. Other than playing with it, I have not used it yet, but it appears to be well made and the fine poles should be handy for small parts. Grip would appear to be good. If I recall correctly, the picture showed a permanenent handle, but mine actually just came with an allen socket (and an included wrench) for engaging and disengaging the magnets. This should address the concerns about a handle being in the way.

Paul

[websterz]

Let us know how the chuck works out. I have been looking for a decent price on a fine pole and at $117 shipped that 6x6 may be exactly what I have been waiting for!!

[oldtiffie]

Enjoy your grinder

Well this old Enco surface grinder is starting to look like I may have it close to working order. The next challenge is a magnetic chuck. Being new to surface grinding, I have no idea of what to look for. I am going to need a 6x18 and that is about the extent of my knowledge. The SG has the capacity for an electro magnetic type. What are the pros and conns of permanent magnet vs electromagnetic? Enco has an import 6x18 permanent magnetic one for @$500. The next step is way over a grand. Ebay has them all over the place, from $300-$3k.

Now this is going to be a hobby machine and my budget is tight ($300-$700). Does anyone have some words or wisdom to help me select an adequate magnetic chuck for this beast?

TIA

Randy

Hi Randy,

I thought I'd pick up where I left off in my previous post in this thread and post some more text as well as pics.

I have included links to the pics rather than images as there are a few of them and I didn't want it to be a PITA to anyone having to wait for the images to load on broad-band - let alone "dial up".

Most will be self-explanatory.

If you need more info, please get back to me by PM or email (in case I miss the post).

These are my magnetic chucks (note handles, fences as well as pretty fine spacing). The "finer" adaptors are only used when I need to hold round or thin - or any stuff - that needs to be held vertically - beats a vice most times!! I always use the chuck fences if I have any doubts about the job slipping on the chuck. Additional this steel strip stops as required are excellent - set them up as a "vee" for round stuff.

http://i200.photobucket.com/albums/a...ticchucks1.jpg

Here is a wheel on a balancing hub as well as the balancing arbor and the shop-made balancing tool and two levels.
http://i200.photobucket.com/albums/a...elbalance3.jpg

http://i200.photobucket.com/albums/a...elbalance1.jpg

I never use the 0.02mm/m 1:50,000 level as I prefer the excellent 0.5mm/m (1:2,000) carpenters level as it is more than accurate enough to balance the wheels. The finer level is a PITA for no real additional benefit.

http://i200.photobucket.com/albums/a...elbalance1.jpg

http://i200.photobucket.com/albums/a...elbalance2.jpg

And here are some others that should be self-explanatory:

http://i200.photobucket.com/albums/a...f_Grinder1.jpg

http://i200.photobucket.com/albums/a..._Grinder1A.jpg

http://i200.photobucket.com/albums/a...f_Grinder2.jpg

http://i200.photobucket.com/albums/a...f_Grinder3.jpg

http://i200.photobucket.com/albums/a...f_Grinder4.jpg

http://i200.photobucket.com/albums/a...uck_block1.jpg

http://i200.photobucket.com/albums/a...ck_block1A.jpg

http://i200.photobucket.com/albums/a...uck_block2.jpg

http://i200.photobucket.com/albums/a...uck_block3.jpg

http://i200.photobucket.com/albums/a...uck_block4.jpg

http://i200.photobucket.com/albums/a...uck_block5.jpg

Hopefully, in the not too distant future, I will post a thread on grinding lathe tools and end mills (sides and ends) quite accurately with a magnetic chuck and a "Spindexer". Your surface grinder can do a lot of work that many would say can only be done on a Tool & Cutter grinder. It may be easier on a T&C grinder but it certainly is not difficult doing a lot of T&C work on your surface grinder.

Once you get used to using your grinder as well as realising what it can do, it will surprise you just how versatile it can be and how often you use it. Sometimes I don't use my grinders for months on end but I sure do both need and appreciate having them when the need arises.

Don't let anyone tell you that the Chinese chucks are rubbish - they certainly are not - mine are excellent - (and all grinder stuff as well as most tools) from "known" dealers in the US who rely on their reputation, pricing and service to get return business, are excellent. A lot of the stuff you see in this post is from LittleMachineShop as well as CDCO Tools and others in the US - but not all. I buy stuff from UK and Europe as well - and lot from "home" - here in OZ. I have never been disappointed in or let down by any of it.

I never buy used precision stuff on eBay - but I am a long way from the US to return any that are sub-standard. BUt that is my choice and I don't want to influence or critise anyone else's choices or method.

I will notify you of this post by PM.

Enjoy your grinder.

[lakeside53]

Where did you get your balancing sleeves from?

[websterz]

How is the holding power and overall quality of the Bostar mag chuck?

[JMS6449]

In 42 years as a toolmakern i have never seen or balanced a 7" or 8" grinding wheel. Install on the grinder, side dress and bottom dress and all is well.

Now 12" wheels are another story.

Also remember to "ring" the wheel as a safety check.